This invention relates to a method for diagnosing the presence of cancer and monitoring the progress of treatment of cancer patients, and more particularly, to a method of assaying the presence and quantity of cancer cells in a patient by quantitation of a circulating marker protein.
The identification of tumor markers has been an important objective of cancer research over the past several decades. Circulating tumor markers, i.e. markers released into the bloodstream, have been sought in particular because there are numerous clinical situations wherein it would be advantageous to detect and/or determine the presence of cancer cells in a patient by quantitation of a tumor marker in a plasma or serum sample derived from whole blood. One situation is a threshhold diagnosis to ascertain if there are any cancer cells in the patient. Another situation arises during treatment when it is very useful to monitor the changes in overall cancer cell presence to evaluate and guide the course of treatment. It is essential that the marker to be assayed for be one which is not secreted or secreted in insignificant amounts by non-cancerous cells. It is additionally of great practical importance, in order that the test have broad usefulness, that the marker to be assayed be one which is secreted by all or at least a large class of cancerous or transformed cells.
Circulating tumor markers such as carcinoembryonic antigen and alpha-fetoprotein are currently used to detect the presence of colon and liver carcinomas, respectively, and more particularly, they are used to monitor the effectiveness of treatment and recurrence of tumor growth. The applicability of carcinoembryonic antigen and alpha-fetoprotein is limited to a few tumor types, however, and no marker has been previously identified that detects a wide variety of tumor types. See generally, Sell, S. Alphafetoprotein. In: S. Sell (ed.) Cancer Markers, pp 249-293. Clifton, N.J.: Humana Press, 1980 and, in the same text, Shively, J. E. and Todd, C. W., Carcinoembryonic antigen A: chemistry and biology, at pp. 295-314.